BackgroundCutaneous squamous cell carcinoma (cSCC) is a significant cause of morbidity for immunosuppressed patients such as organ transplant recipients, however histological parameters which predict the likelihood of tumor progression are typically based on general population studies in which immunosuppressed patients represent only a small fraction of cases. ObjectivesTo determine the histological parameters which have independent prognostic value for cSCC arising in renal transplant recipients. MethodsCase-control study incorporating a retrospective blinded histological review of 70 archived specimens of cSCC diagnosed in renal transplant recipients, comprising 10 cases where the tumor had progressed and 60 controls. ResultsProgression was significantly associated with head and neck location, size, depth, poor histological grade, perineural invasion (including small calibre perineural invasion), lymphovascular invasion and a desmoplastic growth pattern. LimitationsThe retrospective nature and the low number of cases compared to controls. ConclusionIn immunosuppressed patients both small calibre perineural invasion and a desmoplastic growth pattern may also have prognostic significance in addition to other histological parameters already recognised in formal staging schemes.